Conventionally, a dynamometer has been used for testing the running performance of a motor vehicle in a developing field or a production field. There are known various dynamometers, among which is a dynamometer to be connected to a drive shaft of a motor vehicle. Such a dynamometer is, for example, directly connected to a hub of a driving wheel of a motor vehicle, and is subjected to rotational driving force during running from the motor vehicle. The dynamometer detects running performance such as an output, torque, rotational speed, and the like of the motor vehicle in a running state. Such a dynamometer which is connected to a hub is also referred to as a hub-coupled dynamometer. For example, Patent Literature 1 discloses a dynamometer which is connected to a hub of a motor vehicle. The dynamometer according to Patent Literature 1 is provided with a hydraulic pump having an input shaft which is connected to the hub of a motor vehicle. The hydraulic pump rotates with the hub and the drive shaft of the motor vehicle while applying load thereto. The dynamometer detects torque, etc. of the motor vehicle in a running state from output pressure, etc. of the hydraulic pump.